biostudies-literatureGjonlleshaj PNational Institute of Allergy and Infectious DiseasesNatural History MuseumETH ZurichBiotechnology and Biological Sciences Research Council101293https://www.ebi.ac.uk/biostudies/studies/S-EPMC12946758biostudies-literatureUnknown6(2)Somatic cell reprogramming into induced pluripotent stem cells (iPSCs) has been achieved in various mammals; however, assessing iPSC contribution to full-term chimeras beyond laboratory rodents remains challenging. Here, we demonstrate induction of pluripotency in male and female fibroblasts from the African pygmy mouse (APM), one of the smallest mammals. Using transcription factors and small molecules, we derived expandable APM-iPSCs that express pluripotency markers, differentiate into various cell types in vitro, and form gastruloids. Injection of APM-iPSCs into house mouse blastocysts generated full-term interspecies chimeras demonstrating extensive contribution to various tissues, including testicular germ cells. Notably, high APM contribution in organs such as heart and testes correlCell reports methodsAfrican pygmy mouse iPSCs as a model for in vitro embryogenesis, interspecies chimerism, and blastocyst complementation.PMC12946758bioart.niaid.nih.gov/bioart/154BB/R015260/1Taborsky DBundschuh NVeyrunes FTrautmann CLTarnowska-Sengul MGjonlleshaj PAgostinho de Sousa JBar-Nur OSendoel ALenardic AfalseAfrican pygmy mouse iPSCs as a model for in vitro embryogenesis, interspecies chimerism, and blastocyst complementation.Somatic cell reprogramming into induced pluripotent stem cells (iPSCs) has been achieved in various mammals; however, assessing iPSC contribution to full-term chimeras beyond laboratory rodents remains challenging. Here, we demonstrate induction of pluripotency in male and female fibroblasts from the African pygmy mouse (APM), one of the smallest mammals. Using transcription factors and small molecules, we derived expandable APM-iPSCs that express pluripotency markers, differentiate into various cell types in vitro, and form gastruloids. Injection of APM-iPSCs into house mouse blastocysts generated full-term interspecies chimeras demonstrating extensive contribution to various tissues, including testicular germ cells. Notably, high APM contribution in organs such as heart and testes correl2026-01-01T00:00:00Z2026 Feb2026-07-16T22:27:20.11Z2026-07-11T03:11:56.077ZS-EPMC129467584160521710.1016/j.crmeth.2025.101293